270 lines
17 KiB
Markdown
270 lines
17 KiB
Markdown
# socket.io
|
|
[](https://replit.com/@socketio/socketio-minimal-example)
|
|
[](#backers) [](#sponsors)
|
|
[](https://github.com/socketio/socket.io/actions)
|
|
[](https://www.npmjs.com/package/socket.io)
|
|
|
|
[](https://slackin-socketio.now.sh)
|
|
|
|
## Features
|
|
|
|
Socket.IO enables real-time bidirectional event-based communication. It consists of:
|
|
|
|
- a Node.js server (this repository)
|
|
- a [Javascript client library](https://github.com/socketio/socket.io-client) for the browser (or a Node.js client)
|
|
|
|
Some implementations in other languages are also available:
|
|
|
|
- [Java](https://github.com/socketio/socket.io-client-java)
|
|
- [C++](https://github.com/socketio/socket.io-client-cpp)
|
|
- [Swift](https://github.com/socketio/socket.io-client-swift)
|
|
- [Dart](https://github.com/rikulo/socket.io-client-dart)
|
|
- [Python](https://github.com/miguelgrinberg/python-socketio)
|
|
- [.NET](https://github.com/doghappy/socket.io-client-csharp)
|
|
- [Rust](https://github.com/1c3t3a/rust-socketio)
|
|
|
|
Its main features are:
|
|
|
|
#### Reliability
|
|
|
|
Connections are established even in the presence of:
|
|
- proxies and load balancers.
|
|
- personal firewall and antivirus software.
|
|
|
|
For this purpose, it relies on [Engine.IO](https://github.com/socketio/engine.io), which first establishes a long-polling connection, then tries to upgrade to better transports that are "tested" on the side, like WebSocket. Please see the [Goals](https://github.com/socketio/engine.io#goals) section for more information.
|
|
|
|
#### Auto-reconnection support
|
|
|
|
Unless instructed otherwise a disconnected client will try to reconnect forever, until the server is available again. Please see the available reconnection options [here](https://socket.io/docs/v3/client-api/#new-Manager-url-options).
|
|
|
|
#### Disconnection detection
|
|
|
|
A heartbeat mechanism is implemented at the Engine.IO level, allowing both the server and the client to know when the other one is not responding anymore.
|
|
|
|
That functionality is achieved with timers set on both the server and the client, with timeout values (the `pingInterval` and `pingTimeout` parameters) shared during the connection handshake. Those timers require any subsequent client calls to be directed to the same server, hence the `sticky-session` requirement when using multiples nodes.
|
|
|
|
#### Binary support
|
|
|
|
Any serializable data structures can be emitted, including:
|
|
|
|
- [ArrayBuffer](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer) and [Blob](https://developer.mozilla.org/en-US/docs/Web/API/Blob) in the browser
|
|
- [ArrayBuffer](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer) and [Buffer](https://nodejs.org/api/buffer.html) in Node.js
|
|
|
|
#### Simple and convenient API
|
|
|
|
Sample code:
|
|
|
|
```js
|
|
io.on('connection', socket => {
|
|
socket.emit('request', /* … */); // emit an event to the socket
|
|
io.emit('broadcast', /* … */); // emit an event to all connected sockets
|
|
socket.on('reply', () => { /* … */ }); // listen to the event
|
|
});
|
|
```
|
|
|
|
#### Cross-browser
|
|
|
|
Browser support is tested in Sauce Labs:
|
|
|
|
[](https://saucelabs.com/u/socket)
|
|
|
|
#### Multiplexing support
|
|
|
|
In order to create separation of concerns within your application (for example per module, or based on permissions), Socket.IO allows you to create several `Namespaces`, which will act as separate communication channels but will share the same underlying connection.
|
|
|
|
#### Room support
|
|
|
|
Within each `Namespace`, you can define arbitrary channels, called `Rooms`, that sockets can join and leave. You can then broadcast to any given room, reaching every socket that has joined it.
|
|
|
|
This is a useful feature to send notifications to a group of users, or to a given user connected on several devices for example.
|
|
|
|
|
|
**Note:** Socket.IO is not a WebSocket implementation. Although Socket.IO indeed uses WebSocket as a transport when possible, it adds some metadata to each packet: the packet type, the namespace and the ack id when a message acknowledgement is needed. That is why a WebSocket client will not be able to successfully connect to a Socket.IO server, and a Socket.IO client will not be able to connect to a WebSocket server (like `ws://echo.websocket.org`) either. Please see the protocol specification [here](https://github.com/socketio/socket.io-protocol).
|
|
|
|
## Installation
|
|
|
|
```bash
|
|
// with npm
|
|
npm install socket.io
|
|
|
|
// with yarn
|
|
yarn add socket.io
|
|
```
|
|
|
|
## How to use
|
|
|
|
The following example attaches socket.io to a plain Node.JS
|
|
HTTP server listening on port `3000`.
|
|
|
|
```js
|
|
const server = require('http').createServer();
|
|
const io = require('socket.io')(server);
|
|
io.on('connection', client => {
|
|
client.on('event', data => { /* … */ });
|
|
client.on('disconnect', () => { /* … */ });
|
|
});
|
|
server.listen(3000);
|
|
```
|
|
|
|
### Standalone
|
|
|
|
```js
|
|
const io = require('socket.io')();
|
|
io.on('connection', client => { ... });
|
|
io.listen(3000);
|
|
```
|
|
|
|
### Module syntax
|
|
|
|
```js
|
|
import { Server } from "socket.io";
|
|
const io = new Server(server);
|
|
io.listen(3000);
|
|
```
|
|
|
|
### In conjunction with Express
|
|
|
|
Starting with **3.0**, express applications have become request handler
|
|
functions that you pass to `http` or `http` `Server` instances. You need
|
|
to pass the `Server` to `socket.io`, not the express application
|
|
function. Also make sure to call `.listen` on the `server`, not the `app`.
|
|
|
|
```js
|
|
const app = require('express')();
|
|
const server = require('http').createServer(app);
|
|
const io = require('socket.io')(server);
|
|
io.on('connection', () => { /* … */ });
|
|
server.listen(3000);
|
|
```
|
|
|
|
### In conjunction with Koa
|
|
|
|
Like Express.JS, Koa works by exposing an application as a request
|
|
handler function, but only by calling the `callback` method.
|
|
|
|
```js
|
|
const app = require('koa')();
|
|
const server = require('http').createServer(app.callback());
|
|
const io = require('socket.io')(server);
|
|
io.on('connection', () => { /* … */ });
|
|
server.listen(3000);
|
|
```
|
|
|
|
### In conjunction with Fastify
|
|
|
|
To integrate Socket.io in your Fastify application you just need to
|
|
register `fastify-socket.io` plugin. It will create a `decorator`
|
|
called `io`.
|
|
|
|
```js
|
|
const app = require('fastify')();
|
|
app.register(require('fastify-socket.io'));
|
|
app.io.on('connection', () => { /* … */ });
|
|
app.listen(3000);
|
|
```
|
|
|
|
## Documentation
|
|
|
|
Please see the documentation [here](https://socket.io/docs/).
|
|
|
|
The source code of the website can be found [here](https://github.com/socketio/socket.io-website). Contributions are welcome!
|
|
|
|
## Debug / logging
|
|
|
|
Socket.IO is powered by [debug](https://github.com/visionmedia/debug).
|
|
In order to see all the debug output, run your app with the environment variable
|
|
`DEBUG` including the desired scope.
|
|
|
|
To see the output from all of Socket.IO's debugging scopes you can use:
|
|
|
|
```
|
|
DEBUG=socket.io* node myapp
|
|
```
|
|
|
|
## Testing
|
|
|
|
```
|
|
npm test
|
|
```
|
|
This runs the `gulp` task `test`. By default the test will be run with the source code in `lib` directory.
|
|
|
|
Set the environmental variable `TEST_VERSION` to `compat` to test the transpiled es5-compat version of the code.
|
|
|
|
The `gulp` task `test` will always transpile the source code into es5 and export to `dist` first before running the test.
|
|
|
|
|
|
## Backers
|
|
|
|
Support us with a monthly donation and help us continue our activities. [[Become a backer](https://opencollective.com/socketio#backer)]
|
|
|
|
<a href="https://opencollective.com/socketio/backer/0/website" target="_blank"><img src="https://opencollective.com/socketio/backer/0/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/1/website" target="_blank"><img src="https://opencollective.com/socketio/backer/1/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/2/website" target="_blank"><img src="https://opencollective.com/socketio/backer/2/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/3/website" target="_blank"><img src="https://opencollective.com/socketio/backer/3/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/4/website" target="_blank"><img src="https://opencollective.com/socketio/backer/4/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/5/website" target="_blank"><img src="https://opencollective.com/socketio/backer/5/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/6/website" target="_blank"><img src="https://opencollective.com/socketio/backer/6/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/7/website" target="_blank"><img src="https://opencollective.com/socketio/backer/7/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/8/website" target="_blank"><img src="https://opencollective.com/socketio/backer/8/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/9/website" target="_blank"><img src="https://opencollective.com/socketio/backer/9/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/10/website" target="_blank"><img src="https://opencollective.com/socketio/backer/10/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/11/website" target="_blank"><img src="https://opencollective.com/socketio/backer/11/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/12/website" target="_blank"><img src="https://opencollective.com/socketio/backer/12/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/13/website" target="_blank"><img src="https://opencollective.com/socketio/backer/13/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/14/website" target="_blank"><img src="https://opencollective.com/socketio/backer/14/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/15/website" target="_blank"><img src="https://opencollective.com/socketio/backer/15/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/16/website" target="_blank"><img src="https://opencollective.com/socketio/backer/16/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/17/website" target="_blank"><img src="https://opencollective.com/socketio/backer/17/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/18/website" target="_blank"><img src="https://opencollective.com/socketio/backer/18/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/19/website" target="_blank"><img src="https://opencollective.com/socketio/backer/19/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/20/website" target="_blank"><img src="https://opencollective.com/socketio/backer/20/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/21/website" target="_blank"><img src="https://opencollective.com/socketio/backer/21/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/22/website" target="_blank"><img src="https://opencollective.com/socketio/backer/22/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/23/website" target="_blank"><img src="https://opencollective.com/socketio/backer/23/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/24/website" target="_blank"><img src="https://opencollective.com/socketio/backer/24/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/25/website" target="_blank"><img src="https://opencollective.com/socketio/backer/25/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/26/website" target="_blank"><img src="https://opencollective.com/socketio/backer/26/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/27/website" target="_blank"><img src="https://opencollective.com/socketio/backer/27/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/28/website" target="_blank"><img src="https://opencollective.com/socketio/backer/28/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/backer/29/website" target="_blank"><img src="https://opencollective.com/socketio/backer/29/avatar.svg"></a>
|
|
|
|
|
|
## Sponsors
|
|
|
|
Become a sponsor and get your logo on our README on Github with a link to your site. [[Become a sponsor](https://opencollective.com/socketio#sponsor)]
|
|
|
|
<a href="https://opencollective.com/socketio/sponsor/0/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/0/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/1/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/1/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/2/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/2/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/3/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/3/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/4/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/4/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/5/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/5/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/6/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/6/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/7/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/7/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/8/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/8/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/9/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/9/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/10/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/10/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/11/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/11/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/12/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/12/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/13/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/13/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/14/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/14/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/15/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/15/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/16/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/16/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/17/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/17/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/18/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/18/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/19/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/19/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/20/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/20/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/21/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/21/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/22/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/22/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/23/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/23/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/24/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/24/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/25/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/25/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/26/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/26/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/27/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/27/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/28/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/28/avatar.svg"></a>
|
|
<a href="https://opencollective.com/socketio/sponsor/29/website" target="_blank"><img src="https://opencollective.com/socketio/sponsor/29/avatar.svg"></a>
|
|
|
|
|
|
## License
|
|
|
|
[MIT](LICENSE)
|